1. Field
The teachings in accordance with the exemplary embodiments of this present disclosure generally relate to a trip device, and more particularly to a trip device for use in a circuit breaker.
2. Background
Generally, circuit breakers are used to protect electrical circuitry from damage due to an over-current condition, such as an overload condition or a relatively high level short circuit or fault condition by automatically interrupting the circuitry.
The circuit breaker may be largely categorized into three types, based on trip method, that is, a bimetal type which carries out a trip operation by being heated and bent in response to a persistent over-current condition, an electromagnetic field type which operates by sucking a core in response to an electromagnetic field formed on a coil when an over-current flows, and an electronic type which adopts an electronic trip device and a microprocessor.
The electronic trip device is advantageous in that it is not affected by ambient temperatures and little characteristic differences exist among products to provide a frequency characteristic that cannot be embodied by other types of trip devices, such that demands on electronic trip devices increase for important and high-end facilities
Many circuit breakers also use auxiliary trip systems to perform auxiliary functions in addition to intrinsic function of circuit breaker. The auxiliary trip systems can be used in several ways, but are typically used to trip a breaker more rapidly than a primary trip device of the breaker. For example, the most frequently used auxiliary systems include an under-voltage trip device (UVT) and a remotely switchable trip auxiliary device (hereinafter referred to as remote trip device).
The UVT is an auxiliary trip system that detects under-voltage on a circuit if voltage lower than rated voltage is applied to the circuit, thereby automatically tripping the circuit breaker for protecting the circuit. That is, the UVT trips a circuit breaker when a load or a voltage on a line drops by 20%˜70% below a reference voltage or when there occurs a blackout to prevent damage to the load or to the line from over-current during return to original voltage. The UVT includes therein a trip coil and electronic circuit.
The remote trip device is an auxiliary trip system capable of performing a remotely switchable trip function when a circuit breaker needs an emergent trip function due to abnormalcy on a load or on a line. The remote trip device includes therein a trip coil.
Now, a process of coupling an auxiliary trip system such as UVT or a remote trip device to an electromagnetic field type circuit breaker will be described with reference to FIG. 1.
FIG. 1 is a schematic view illustrating a coupled structure of an auxiliary device to a circuit breaker according to prior art.
In order to conventionally couple an auxiliary device (120) such as an UVT or a remote trip device to a circuit breaker, a user must open an auxiliary cover (110) rotatably mounted on a breaker cover (100) and personally mount the auxiliary device (120) to the circuit breaker.
To be more specific, when a user first unscrews a bolt (130) fastened to a side of the auxiliary cover (110) using a screw driver and rotates the auxiliary cover to one direction, the auxiliary cover (110) is opened as one side of the auxiliary cover (110) is hinged to the cover (100), as shown in FIG. 1.
At this time, a pair of fastening grooves (140) is formed respectively on right and left upper sides of the cover (100) to allow a standardized size of auxiliary device (120) to be inserted, where the user inserts and couples the auxiliary device to the grooves (140).
The conventional circuit breaker thus configured is disadvantageous in that both the UVT and the remote trip device as auxiliary devices must be equipped to detect an under-voltage on a circuit if a voltage lower than a rated voltage is applied to the circuit and to remotely trip a remote accident.
There is thus a need for a trip device that requires a fewer auxiliary trip systems, less energy and inconvenience for operation and that is less in cost.